Magnetic tape cassette with guard panel

ABSTRACT

A magnetic tape cassette having two symmetrical sides and which includes a cassette body having shaft-receiving holes formed respectively in right and left walls of the cassette body in such a manner that the holes are elongated in the front-to-rear direction of the cassette body. A substantially U-shaped guard panel is provided having rotary shafts on both ends engaged with the elongated holes so that the guard panel can be swung about the rotary shafts. A spring is connected between the cassette body and the guard panel to urge the latter to close the opening formed in the front wall of the cassette body.

BACKGROUND OF THE INVENTION

The present invention relates to a magnetic tape cassettes, and moreparticularly to a compact magnetic tape cassette substantially equal insize to so-called Philips-type magnetic tape cassette.

Recently, cassette tape recorders have been remarkably reduced both insize and in weight. Accordingly, there has been a strong demand for theprovision of a magnetic tape cassette which is small in size and whichis suitable for signal recording and reproducing operations with highquality and high density and which has a long playing time.

Heretofore, in the use of a compact cassette with an audio device,analog signals have most commonly been employed for recording andreproducing operations. However, in the analog system, the density ofsignal recording is limited. On the other hand, it is well known in theart that a digital system such as a pulse code modulation system inwhich input signals are converted into pulses for recording andreproducing permits recording with a high density and without distortionby signal communication paths and the recording medium.

Recently, there has been developed a magnetic head with whichmulti-track signal recording and reproducing operations can be performedwith a magnetic tape whose width is as small as that of the magnetictape of a Philips cassette. As a result, it is possible to carry outmulti-track signal recording and reproducing operations with a magnetictape cassette which is as compact as the Philips-type cassette.

In the case where a multi-track signal recording operation is carriedout with a compact cassette in a fixed magnetic head system, forinstance, in a case of using thirty-six tracks for recording signals,the width of each track is of the order of 100 microns, which isextremely small when compared with the width of each track in afour-track signal recording operation using a standard Philips-typecassette. Accordingly, the effective area of the surface of the magnetichead which is brought into contact with each track is considerablysmall. Therefore, if dust stuck to the magnetic tape lodges in the gapbetween the magnetic tape and the magnetic head, then the recording andreproducing characteristics are greatly affected.

On the other hand, a video tape cassette operated with a rotary magnetichead system is extensively employed for high-density signal recording.The video tape cassette has a rockable guard panel over the openingformed in the front wall thereof to protect the magnetic tape fromdamage and to prevent dust from affecting the high-density signalrecording and reproducing characteristics.

In more detail, ABS resin or PS resin is most extensively employed toform the above-described magnetic tape cassette. However, when the guardpanel is swung back and forth, it slides on the cassette case, forming apowder of the resin. Since the guard panel is swung to open and closethe opening formed in the front end wall of the cassette case, the resinpowder is produced near the opening. Accordingly, the resin powder thusproduced is liable to enter the cassette case through the opening, thusadversely affecting the signal recording and reproductioncharacteristics of the magnetic tape.

In the rotary magnetic head system, in general, the signal recording andreproducing operations are carried out with the magnetic tape run in onedirection. Thus, in the magnetic tape cassette, it is unnecessary thatboth sides (sides A and B) thereof be symmetrical in structure.Furthermore, in the rotary magnetic head system, in general, twomagnetic heads are inclined at certain angles with respect to the taperunning direction and alternately contact the magnetic tape while beingrotated. This has the effect of sweeping dust away from the magnetictape. Therefore, the effect of dust on the signal recording andreproducing characteristics is relatively small when compared with thatof dust on the characteristic in the fixed magnetic head system.

A magnetic tape cassette to which the technical concept of the inventionis applied is one which is operated in the fixed magnetic head systemand has two sides (sides A and B) with cassette case upper and lowerhalves which are symmetrical in configuration. In the fixed magnetichead system, as explained above, dust adversely affects the signalrecording and reproducing characteristic more than in the case of arotary magnetic head system. Therefore, the guard panel of the magnetictape cassette should have a more effective dust-proofing effect thanthat of the aforementioned video tape cassette.

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a magnetic tapecassette in which the guard panel has a positive dust-proofing effect,the upper and lower halves of the cassette case are symmetrical instructure, and which can be used for multi-track signal recording andreproducing operation.

A further object of the invention is to provide a magnetic tape cassettein which the guard panel is completely locked at the closed positionwhen the cassette is not in use, thereby to improve the dust-proofingeffect, and which has two sides symmetrical in configuration andconstruction so as to be usable for a multi-track signal recording andreproducing operation.

Yet another object of the invention is to provide a novel magnetic tapecassette which has a guard panel adapted to open and close an openingformed in the front end wall of the cassette case and which is designedto minimize the production of resin powder when it is swung to rub thecassette case, and both sides (A and B sides) of which can be used for amulti-track signal recording or reproducing operation.

The foregoing object and other objects of the invention have beenachieved by the provision of a magnetic tape cassette which has amagnetic head inserting opening in the front wall of a cassette bodyincorporating a pair of hubs on which a magnetic tape is wound, inwhich, according to the invention, the cassette body has rotary-shaftreceiving holes elongated in the front-to-rear direction of the cassettebody respectively in the right and left walls of the cassette body, andthe cassette includes a guard panel for closing the opening, the guardpanel being substantially U-shaped and having two rotary shafts whichare engaged with the elongated holes in such a manner that the guardpanel is swingable about the rotary shafts, and an elastic memberconnected between the guard panel and the cassette body to urge theguard panel to close the opening. The sides of the cassette aresymmetrical in construction.

The foregoing object and other objects of the invention have also beenachieved by the provision of a magnetic tape cassette having a magnetichead inserting opening in the front wall of a cassette bodyincorporating a pair of hubs on which a magnetic tape is wound, which,according to the invention, includes a cassette body having rotary shaftreceiving grooves respectively in the front end portions of the rightand left side walls thereof, each rotary shaft receiving groove havingtwo inclined walls which converge towards the front of the cassette bodyand which are symmetrical in configuration with respect to a line whichdivides the side walls into the upper and lower parts; a guard paneladapted to close the opening and which is substantially U-shaped inhorizontal section, the guard panel having rotary shafts extending fromthe inner surfaces of right and left end pieces thereof in such a mannerthat the guard panel is swingable about the rotary shafts which areengaged with the rotary shaft receiving grooves; and urging meansprovided on one of the right and left side walls and connected to a partof the end piece which is closer to the cassette body than the rotaryshaft, thereby to urge the guard panel towards the cassette body. Thetwo sides of the cassette are symmetrical in configuration.

Still further, the objects of the invention have been achieved by theprovision of a magnetic tape cassette having a magnetic head insertingopening in the front end wall of a cassette case incorporating a pair ofhubs on which a magnetic tape is wound, wherein according to theinvention, the improvement comprises: a cassette case having a slidegroove and an arcuate guide groove formed in each of the right and leftside walls of the cassette case in such a manner that the grooves arebehind the opening and the slide groove extends in the front-to-reardirection of the cassette and intersects the guide groove at the middlethereof; a guard panel substantially U-shaped in vertical section, theguard panel having a pair of end pieces at opposite ends, each of theend pieces haing first and second supporting shafts which are arrangedon a line extending in the front-to-rear direction of the cassette andare engaged with the slide groove and guide groove, the guard panelbeing swingable vertically of the cassette and adapted to close theopening; and an elastic member connected to the guard panel to cause theguard panel to close the opening, wherein the two sides of the cassetteare symmetrical in configuration and construction.

The foregoing objects of the invention have further been achieved by theprovision of a magnetic tape cassette having a magnetic head insertingopening formed in the front end wall of the cassette case incorporatinga pair of hubs on which a magnetic tape is wound, wherein theimprovement, according to the invention comprises: a cassette casehaving shaft-receiving through-holes in front end portions of right andleft side walls thereof, each shaft-receiving through-hole being in theform of an "L" inclined forwardly with the upper and lower halvesthereof being symmetrical in configuration with respect to a line whichdivides the respective side wall into the upper and lower halves; aguard panel substantially U-shaped in horizontal section, the guardpanel comprising right and left end pieces with rotating shafts whichare slidably engaged with respective ones of the shaft-receivingthrough-holes, each rotating shaft having a base part and an end partwhich are each in the form of a flange having a diameter larger than thewidth of the shaft-receiving through-holes so that the guard panel isswingable vertically of the cassette and adapted to close the opening;and a tension spring provided on at least one of the right and left sidewalls of the cassette case and connected to the end piece at theposition which is closer to the cassette case than the rotating shaft ofthe end piece to urge the guard panel towards the cassette case. The twosides of the cassette and symmetrical in configuration and constructionso that the guard panel is swung with the rotating shafts being slidalong the shaft-receiving through-holes.

The invention can also be practiced by the provision of a magnetic tapecassette having a magnetic head inserting opening in the fron end wallof a cassette case incorporating a pair of hubs on which a magnetic tapeis wound, and a guard panel substantially U-shaped in horizontal sectionand adapted to close the opening, in which, according to the invention,the cassette case has a pair of shaft-receiving holes respectively inthe front end portions of the right and left side walls of the cassettecase, the shaft-receiving holes receive a pair of respective rotatingshafts which extend from both end pieces of the guard panel and arecovered with sleeves made of a material high in wear resistance, and theguard panel is maintained urged towards the cassette case by urgingmeans which is provided on at least one of the right and left side wallsof the cassette case. The two sides of the cassette are symmetrical inconfiguration and in construction.

The foregoing objects of the invention still further have been achievedby the provision of a magnetic tape cassette having a magnetic headinserting opening in the front end wall of a cassette case incorporatinga pair of hubs on which a magnetic tape is wound, wherein according tothe invention, the improvement comprises: a cassette case having upperand lower slopes which are formed by symmetrically chamfering at leastparts of the upper and lower edges of the front end wall, andshaft-receiving holes formed in the outer surfaces of the front endportions of the right and left side walls of the cassette case; a guardpanel substantially U-shaped in horizontal section which comprises rightand left end pieces and a front piece having upper and lower edgesextending towards the cassette case so as to be engaged with the upperand lower slopes, respectively, the guard panel being swingable onrotating shafts which extend from the inner surfaces of the right andleft end pieces to engage with respective ones of the shaft-receivingholes so that the guard panel can thus open and close the opening; andurging means provided on at least one of the right and left side wallsof the cassette case and connected to the respective end piece at aposition which is closer to the cassette case than the rotating shaft ofthe respective end piece to urge the guard panel towards the cassettecase. Again, the two sides of the cassette case are symmetrical inconfiguration and in construction.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is an exploded perspective view showing a magnetic tape cassetteaccording to this invention;

FIGS. 2A to 2C are explanatory diagrams for a description of theoperation of the magnetic tape cassette of the invention;

FIG. 3 is an exploded perspective view of a magnetic tape cassette of asecond embodiment of the invention;

FIGS. 4 and 5 are an exploded perspective view and an exploded sideview, respectively, showing essential portions of the embodiment of FIG.3;

FIG. 6 is an exploded perspective view showing a third example of amagnetic tape cassette according to the invention;

FIGS 7A to 7C are explanatory diagrams for a description of theoperation of the cassette shown in FIG. 6;

FIG. 8 is a perspective view showing a part of another example of themagnetic tape cassette according to the ivention;

FIG. 9 is an exploded perspective view showing a fourth embodiment ofthe invention;

FIGS. 10 and 11 are an enlarged perspective view and an enlargedhorizontal sectional view, respectively, showing essential parts of theembodiment of FIG. 9;

FIG. 12 is a diagrammatic side view for a description of the operationof a guard panel in FIG. 9;

FIG. 13 is an exploded perspective view showing a fifth embodiment of amagnetic tape cassette according to the invention;

FIG. 14 is an enlarged exploded perspective view showing essential partsof a guard panel shown in FIG. 13;

FIGS. 15 and 16 are an enlarged perspective view and a diagrammatic sideview, respectively, for a description of the operation of the guardpanel in FIG. 13;

FIG. 17 is an enlarged perspective view showing a modification ofsleeves in the magnetic tape cassette according to the fifth embodiment;

FIG. 18 is an exploded perspective view showing a sixth embodiment of amagnetic tape cassette according to the invention;

FIG. 19 is a vertical sectional view showing essential parts of thecassette of FIG. 18;

FIGS. 20 and 21 are diagrammatic side views for a description of theoperation of a guard panel shown in FIGS. 18 and 19; and

FIG. 22 is a perspective view showing a modification of the guard panelof the cassette according to the sixth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a magnetic tape cassette 1 according to a firstembodiment of the invention is a compact cassette which is substantiallythe same in size as a conventional Philips-type cassette. The cassette 1has a cassette case or body 2 with symmetricl upper and lower halves andwith an opening 3 in the front wall thereof. A guard panel 4 adapted toclose the opening 3 is coupled to the cassette body 2 in such a mannerthat it is swingable vertically of the cassette. The opening 3 isadapted to receive the recording and reproducing head, the erasing headand the pinch roller of a magnetic tape recording and reproducingdevice.

A magnetic tape T wound on a pair of hubs (not shown) is accommodated inthe cassette body 2 in such a manner that it can run along the opening3. The hubs are arranged in correspondence to a pair of shaft insertionholes 5 into which the drive shafts of the magnetic tape recording andreproducing device are inserted. Furthermore, a shield plate forshielding a magnetic tape from external noise in a recording orreproducing operation and a pressure pad for positively bringing themagnetic tape T into contact with the magnetic heads are provided at theopening 3 in a conventional manner.

The guard panel 4 is made up of a front wall 6 and right and left endpieces 7. The guard panel 4 is substantially U-shaped in horizontalsection. Rotary shafts 8a and 8b extend from the end pieces 7 towardsthe cassette body so that when these rotary shafts are engaged with thecassette body, the opening 3 is closed by the guard panel 4. That is,the guard panel 4 is coupled through the rotary shafts 8a and 8b to thecassette body 3 in such a manner that it opens and closes the opening 3when swung up and down. The rear end portions 9 of the two end pieces 7have arcuate edges which are curved about the rotary shafts 8a and 8b.

The front portions of the right and left walls 10 of the cassette body 2are set inwardly to form steps 11. Rotary shaft-receiving holes 12 areformed in the steps 11 at the centers in such a manner that they areelongated in the front-to-rear direction of the cassette and along theplane which divides the cassette body into the upper and lower halves.When the guard panel 4 is coupled to the cassette body 2, the rotaryshafts 8a and 8b are engaged with respective ones of the elongated holes12 in such a manner that they are slidable along the elongated holes.

In order for the guard panel 4 to be turned equally both in an upwarddirection and in a downward direction, the upper and lower halves of theguard panel 4 are symmetrical.

The rotary shaft 8b of the guard panel 4 has an end portion 13 which isbent backwardly of the cassette, thus forming a swing arm. A tensionspring 14 arranged inside the cassette body is connected to the endportion 13 of the rotary shaft 8b, thus pulling the guard panel 4backwardly of the cassette. When the guard panel 4 closes the opening 3,the rotary shafts 8a and 8b are positioned at the rear ends of theelongated holes 12, as a result of which the guard panel 4 is positivelyurged to close the opening 3 of the cassette body 2.

The cassette body 2, like a conventional one, may be made of plasticresin such as ABS resin or polyacetal; that is, the material of thecassette body is not particularly limited. The guard panel 4 may be madeof plastic resin such as polyacetal or metal; however, it is desirablethat the material of the guard panel be elastic to the extent that theguard panel 4 can be readily coupled to the cassette body 2.

The magnetic tape T may be a ferromagnetic iron oxide tape or chromiumdioxide tape; however, it is preferable to use a metal tape or a vacuumdeposition tape which is suitable for high-density recording andreproducing.

When the magnetic tape cassette thus constructed is loaded in therecording and reproducing device, the guard panel 4 is swung upwardly bya guard panel swinging mechanism provided in the cassette insertionsection. The guard panel mechanism is composed of a bar-shaped openingmember 15 and a slide member 16. The opening member 15 is abuttedagainst the lower edge of the guard panel near the front end portion ofthe end piece 7 to raise the guard panel. The slide member 16 is broughtinto sliding contact with the arcuate edge of the rear end portion 9 ofthe end piece 7 so as to gradually slide the guard panel 4 forwardly ofthe cassette. Since the rear end portions 9 have arcuate edges which arecurved about the rotary shafts 8a and 8b as described above, the slidemember 16 is slidably in contact with the right rear end portion 9 atthe same position even when the guard panel 4 is fully opened.

The operation of the guard panel 4 by the guard panel swinging mechanismwill be described with reference to FIG. 2 in more detail.

As the magnetic tape cassette 1 is inserted into the cassette insertionsection (in the direction of the arrow X), it is moved downwardly (inthe direction of the arrow Y) as shown in FIG. 2A. As the cassette 1 ismoved downwardly in this manner, the guard panel 4 is enagaged with theopening member 15 and the slide member 16 so that the guard panel 4 isgradually pushed upwardly by the opening member 15 and the slide member16. More specifically, first the slide member 16 is inserted into thecassette as if to push up the rear end portion 9, as a result of whichthe rotary shafts 8a and 8b of the guard panel 4 are moved forwardly tothe front ends of the respective elongated holes 12; i.e., the guardpanel 4 is moved forwardly as shown in FIG. 2B. At the same time, as theopening member 15 is abutted against the lower edge of the guard panel4, the latter is turned about the rotary shafts 8a and 8b upwardly (inthe direction of the arrow Z) as shown in FIG. 2C. As a result, theopening 3 of the cassette body 2 is opened to permit the signalrecording or reproducing operation of the magnetic tape T.

In unloading the magnetic tape cassette 1 from the recording andreproducing device, the cassette 1 is moved in the reverse direction.That is, the cassette 1 is moved upwardly to disengage from the slidemember 16 and the opening member 15 while the tension spring 14 acts tocause the guard panel 4 to completely close the opening 3.

In a magnetic tape cassette whose both sides (sides A and B) are used,the guard panel should be swung symmetrically both in an upwarddirection and in a downward direction. This requirement can be readilysatisfied by displacing the rotary shafts of the guard panel accordingto the invention.

In the magnetic tape cassette 1 of the invention, the guard panel 4 canbe readily swung both in an upward direction and in a downward directionby displacing the rotary shafts of the guard panel. Accordingly, thecassette 1 of the invetion is suitable for multi-track recording andreproducing operations in which both sides (sides A and B) are used withfixed heads.

When the magnetic tape cassette 1 is unloaded from the recording andreproducing device, the elastic member 14 causes the guard panel 4 tocompletely close the opening 3 of the cassette body 2. Therefore, theguard panel 4 protects the magnetic tape T laid along the opening 3 fromdamage and prevents the entrance of dust through the opening 3. That is,the recording and reproducing characteristics of the tape T aremaintained unchanged.

Furthermore, according to the invention, the guard panel 4 is opened bythe guard panel swinging mechanism, which is extremely simple inconstruction. Therefore, employment of the magnetic tape cassette of theinvention will not make the recording and reproducing device intricatein construction.

It has been stated that the technical concept of the invention isapplied to a magnetic tape cassette which is substantially equal in sizeto the compact cassette. However, it should be noted that the technicalconcept of the invention is applicable to other various magnetic tapecassettes.

The invention will be further described with reference to a secondembodiment shown in FIGS. 3 through 5 of the accompanying drawings.

FIG. 3 is an exploded perspective view showing a second embodiment ofthe invention of a magnetic tape cassette, and FIG. 4 is an enlargedperspective view showing the essential components of the cassette. Itshould be noted that, as conductive to an understanding of thisembodiment, FIG. 3 shows the magnetic tape cassette with its guard panelsuitably cut.

In FIG. 3, the magnetic tape casette 21 is substantially equal in sizeto the conventional Philipstype cassette. The magnetic tape casette hasa cassette body 22 composed of the upper and lower halves. The cassettebody 22 has an opening 23 formed in its front wall and a pair of holes36 penetrating the cassette body 22 vertically. The guard panel 24 isadapted to close the opening 23, and is coupled to the cassette body insuch a manner that it is swingable vertically. The recording andreproducing head, the erasing head and the pinch roller of a magnetictape recording and reproducing device are inserted into the opening 23,and capstans are inserted into the holes 36.

A magnetic tape T wound on a pair of hubs (not shown) is accommodated inthe cassette body 22 in such a manner that it can run along the opening23. The hubs are arranged in correspondence to a pair of shaft insertionholes 25 in a conventional manner into which the drive shafts of themagnetic tape recording and reproducing device are inserted.Furthermore, a shield plate for shielding a magnetic tape from externalnoise in recording or reproducing operations and a pressure pad forpositively bringing the magnetic tape T into contact with the magneticheads may be provided at the opening 23 in a conventional manner.

The guard panel 24 is made up of a front wall 26 and right and left endpieces 27. The guard panel 24 is substantially U-shaped in horizontalsection. Rotary shafts 28 extend from the end pieces 27 towards thecassette body so that, when these rotary shafts are engaged with thecassette body, the opening 23 is closed by the guard panel 24. The guardpanel 24 is pulled towards the cassette body by a tension spring 35which is connected between one of the right and left side walls 29 ofthe cassette body and the corresponding end piece 27, and the guardpanel 24 is coupled to the cassette body 22 in such a manner that it isswingable vertically of the cassette body.

In the cassette body 22, the front end portions of the side walls 29 areset inwardly to form steps 30. A spring accommodating groove 33 isformed in the side wall 29 in such a manner that it is flush with thestep 30 and extends from the step 30 towards the back of the cassettebody along the central line which divides the side wall 29 into twoequal parts. Shaft-receiving grooves 31 are formed in the surfaces ofthe steps 30. Each shaftreceiving groove is L-shaped, consisting of twoinclined walls 32 which diverge towards the front of the cassette bodyand which are symmetrical with respect to the central line which dividesthe side wall 29 into two parts.

Cuts 37 are formed at both corners of the front of the cassette body 22,extending in the widthwise direction of the cassette body 22.

One end of the tension spring 35 is connected to the rear end of the endpiece 27 (the right one in FIG. 3), while the other end is locked to aprotrusion 34 formed at the rear end of the spring accommodating groove33 so that the guard panel 24 is pulled towards the cassette body at alltimes. When the guard panel 24 closes the opening, the rotary shafts 28are positioned at the intersection of the inclined walls 32.

The cassette body 22, like a conventional one, may be made of plasticresin such as polyacetal or ABS resin; that is, the material of thecassette body is not particularly limited. The guard panel 24 may bemade of plastic resin such as polyacetal or metal; however, it isdesirable that the material of the guard panel be elastic to the extentthat the guard panel 24 can be readily coupled to the cassette body 22.

The magnetic tape T may be a ferromagnetic iron oxide tape or chromiumdioxide tape; however, it is preferable to use a metal tape or a vacuumdeposition tape which is suitable for high-density recording andreproducing.

When the magnetic tape cassette thus constructed is loaded in arecording and reproducing device, the guard panel 24 is swung upwardlyby a guard panel swinging member 40 provided in the cassette insertionsection. The operation of the guard panel 24 by the guard panel swingingmember 40 will be described with reference to FIG. 5.

The guard panel swinging member 40 is like a plate which is engaged withone of the two ends of the guard panel 24, and it is provided at theinner corner of the cassette insertion section. When the magnetic tapecassette 21 is inserted into the cassette insertion section (in thedirection of the arrow A), it is moved downwardly (in the direction ofthe arrow B). In this operation, the lower edge of the front wall 26 isabutted against the top of the swinging member 40 in such a manner thatthe top of the swinging member 40 confronts with the cut 37 describedabove. As the magnetic tape cassette 21 is further moved (in thedirection of the arrow B), the guard panel 24 is swung (in the directionof the arrow C) while the rotary shaft 28 is moved upwardly along theinclined wall 32. In this operation, the guard panel 24 is swung whilethe inner surface of the front wall 26 is kept in contact with the upperedge of the front wall of the cassette body 22. When the magnetic tapecassette 21 has been loaded (being moved in the direction of the arrowB), the guard panel is held swung upwardly by the guard panel swingingmember 40, thus opening the opening 23.

The upper end face of the guard panel swinging member 40 is suitablyinclined so that, when the guard panel 24 has been swung upwardly, theguard panel 24 may not be displaced towards the cassette body by theelastic force of the tension spring 35.

After the guard panel has been swung upwardly to expose the opening 23,a signal recording or reproducing operation can be performed with themagnetic tape T.

In unloading the magnetic tape cassette from the recording andreproducing device, the cassette 21 is moved in the reverse direction,so that the guard panel swinging member 40 is disengaged from the guardpanel 24. As a result, the guard panel 24 is moved by the force of thetension spring 35 (in a direction opposite to the direction of the arrowC), thus closing the opening 23.

The magnetic tape cassette 21 is so designed that both sides thereof aresymmetrical in construction. Therefore, even when it is loaded to usethe opposite side, the guard panel 24 is operated in the same manner.That is, both sides (sides A and b) of the cassette 21 can be used forsignal recording and reproducing.

In the above-described second embodiment, the guard panel is swung asthe magnetic tape cassette 21 is moved (in the direction of the arrowB). However, the magnetic tape cassette 21 of the invention may be usedwith a magnetic tape recording and reproducing device which is sodesigned that the guard panel swinging member 40 is moved vertically.

In the magnetic tape cassette of the invention, it is not alwaysnecessary that each shaft-receiving groove 31 be L-shaped; that is, allthat is necessary for the shaft-receiving groove is to have at least oneinclined wall 32. It goes without saying that the shaftreceiving groovesmay penetrate the steps 30.

As is apparent from the above description, the magnetic tape cassette ofthe invention includes the guard panel which can be swung both in theupward direction and in the downward direction. Therefore, the cassetteis suitable for multi-track recording and reproducing operations inwhich both sides (sides A and B) are used in fixed head system.

Immediately after the magnetic tape cassette 21 is unloaded from therecording and reproducing device, the guard panel 24 completely closesthe opening 23. Therefore, the guard panel effectively protects themagnetic tape T laid along the opening 23 from damage and prevents theentrance of dust through the opening. That is, the recording andreproducing characteristics of the tape T are maintained unchanged.

Furthermore, according to the invention, the guard panel 24 is swung bythe guard panel swinging member 40 which is extremely simple inconstruction. Therefore, employment of the magnetic tape cassette of theinvention will not make the recording and reproducing device intricatein construction.

The invention will be further described with reference to a thirdembodiment shown in FIGS. 6 through 8 of the accompanying drawings.

The magnetic cassette case 1 shown in FIG. 6 is a compact magnetic tapecassette which is substantially equal in size to the conventionalPhilips-type magnetic tape cassette. A rectangular opening 43 is formedin the front end wall of the cassette case body 42 of the cassette. Aguard panel 44 adapted to close the opening 43 is coupled to thecassette case body in such a manner that it is swingable vertically ofthe cassette. The opening 43 receives the recording and reproducinghead, the erasing head and the pinch roller of a magnetic tape recordingand reproducing device.

A magnetic tape T wound on a pair of hubs (not shown) is laid in thecassette case body 42 in such a manner that it can run along the opening43. The pair of hubs are positioned at a pair of shaft insertion holes45 in a conventional manner into which the drive shafts of the recordingand reproducing device are inserted. A shield board for protecting themagnetic tape from external noise and a leaf spring (not shown) with apressure pad adapted to positively bring the magnetic tape into contactwith the magnetic head during signal recording and reproducingoperations are provided at the opening 43 in the conventional manner.

The guard panel 44 is made up of a front piece 46 and two end pieces 47,being substantially U-shaped in section. Each of the two end pieces 47has a first supporting shaft 48 and a second supporting shaft 49 whichare utilized to allow the guard panel to swingably close the opening 43.The first and second supporting shafts 48 and 49 extend inwardly of thecassette, and are arranged in the front-to-rear direction of thecassette in such a manner that the second supporting shafts 49 arecloser to the cassette case body 42 than the first supporting shafts 48.The guard panel 44 is coupled to the cassette case body so as to openand close the opening 43 while swinging vertically of the cassette. Inorder to swing the guard panel 44 both upwardly and downwardly, theupper and lower halves of the guard panel 44 are made symmetrical, andthe rear edge 50 of each of the end pieces 47 of the guard panel 44 isoutwardly curved about the first supporting shaft 48.

The front end portions of the right and left side walls 51 of thecassette case body 42 are set back inwardly of the cassette to formsteps 52. A slide groove 53 and a guide groove 54 are formed in thesubstantially central portion of each step 52 extending in thefront-to-rear direction of the cassette, and the guide groove 54 extendsacross the slide groove 53 at the middle. The slide groove 53 and eachguide groove 54 are symmetrical with respect to the line which dividesthe side wall 51 into upper and lower halves. The guide grooves 54 arecurved backwardly of the cassette. The guard panel 44 is coupled to thecassette case body 42 in such a manner that the first supporting shafts49 are movable along the slide grooves 53 and the guide grooves 54.

One end of a tension spring 55 arranged inside the cassette case body isconnected to one of the second supporting shafts 49 and the other end isconnected to pin (not shown) provided inside the cassette case body sothat the guard panel 44 is maintained pulled backwardly of the cassette.When the guard panel 44 closes the opening 43, the second supportingshafts 49 abut against the rear ends of the slide grooves 53 and thefirst supporting shafts 48 are positioned in the slide grooves 53. Inthis case, each end piece 47 of the guard panel 44 is held by two pointson the line which extends in the front-to-rear direction of the cassetteso that the guard panel is positively locked to close the opening 43.

The material of the cassette case body 42 is not particularly limited;that is, it may be a plastic resin such as polyacetal or ABS resin whichis heretofore used to form the cassette case body. The guard panel 44may be made of plastic resin such as polyacetal or metal; however, it isdesirable that it be made of a material which is suitably elastic sothat the guard panel 44 can be readily coupled to the cassette case body42.

The magnetic tape T may be a ferromagnetic iron oxide or chromiumdioxide tape; however, it is preferable to use a metal tape orvacuum-deposited tape suitable for a high-density signal recording andreproducing operation.

When the magnetic tape cassette 41 thus constructed is loaded in themagnetic tape recording and reproducing device, the guard panel 44 isswung upwardly by a panel opening mechanism. The panel opening mechanismis made up of a bar-shaped opening member 56 (FIGS. 7A to 7C) and aslide member 57 (FIGS. 7A to 7C). The opening member 56 is abuttedagainst the lower edge of the front end portion of the end piece 47 ofthe guard panel 44 to push the latter upwardly. The slide member 57 isinserted into the cassette while contacting the rear edge 50 of thepiece 47 to gradually slide the guard panel 46 forwardly of thecassette.

The operation of the guard panel 46 of the panel opening mechanism willbe described with reference to FIGS. 7A to 7C.

As the magnetic tape cassette 41 is inserted into the cassette insertionsection (by moving it in the direction of the arrow X) (FIG. 7A), thecassette 41 is moved downwardly (in the direction of the arrow Y). Theopening member 56 and the slide member 57 are arranged below thecassette 41 so that, as the cassette 41 is moved downwardly, the members56 and 57 push the cassette 41 upwardly. That is, the slide member 57,which is inserted in the cassette while contacting the rear edge of theend piece 57, is arranged so as to push the guard panel 44 forwardly ofthe cassette by utilizing the curvature of the rear edge 50 of the endpiece 47. As the guard panel 44 is pushed forwardly of the cassette bythe slide member 57, the first and second supporting shafts 48 and 49 inthe slide grooves 53 are also moved forwardly of the cassette (FIG. 7B).When the guard panel is fully pushed, the first supporting shafts 48 arecaused to abut against the front ends of the slide grooves while thesecond supporting shafts 49 are caused to come to the intersections ofthe slide grooves 53 and the guide grooves 54. The opening member 56,which is adapted to engage with the lower edge of the guard panel,swings the guard panel 44 upwardly (in the direction of the arrow Z)with the first supporting shafts 48 as rotating shafts and with thesecond support shafts 49 as opening slide shafts moving along the guidegrooves 54 (FIG. 7C). When the guard panel 44 is fully swung, the secondsupporting shafts 49 are caused to abut against the ends of the guidegrooves 54.

When the guard panel 44 is swung above the cassette case body asdescribed above, the opening 43 is opened to permit the signal recordingor reproducing operation of the magnetic tape T. In unloading themagnetic tape cassette 41 from the recording and reproducing device, thecassette 41 is moved upwardly, with strokes opposite to those in thecassette loading operation so that the slide member 57 and the openingmember 56 are disengaged from the cassette, while the tension spring 55causes the guard panel 44 to completely close the opening 43.

FIG. 8 shows another example of a magnetic tape cassette according tothis embodiment.

In this example, the position of each guide groove 59 formed in thecassette case body 58 is different from that of the guide groove in FIG.6. That is, the guide groove 59, which is arcuate, intersects a slidegroove 60 at the front end which extends in the front-to-rear directionof the cassette, similarly to the above-described slide groove 53. Theslide groove 60 and the guide groove 59 are symmetrical in configurationwith respect to the line which divides the side wall into the upper andlower halves. The guide groove 59 is curved forwardly of the cassette.The guard panel 64 of the cassette is similar to the guard panel 44 inFIG. 6 except that the rear edge 61 of each end piece is outwardlycurved about a second supporting shaft 62. The second supporting shafts62 and the first supporting shafts 63 of the guard panel 64 are fittedin the slide grooves 60 and the guide grooves 59. When the cassette thusconstructed is loaded in the recording and reproducing device, the guardpanel 64 is swung with the first supporting shafts 63 as opening slideshafts and with the second supporting shafts 62 as rotating shafts.

As described above, in order to prevent the high-density signalrecording magnetic tape cassette 41 from being adversely affected bydust, the guard panel 44 (or 64) should positively close the opening 43of the cassette case. This requirement can be readily satisfied bysupporting the two supporting shafts 48 and 49 (or 62 and 63) of eachend piece on the line extending in the front-to-rear direction of thecassette.

The two supporting shafts 48 and 49 (or 62 and 63) extend from each endpiece of the guard panel in such a manner that they can slide along theguide groove 54 (or 59) and the slide groove 53 (60), and the guardpanel 44 (or 64) is swung with the first supporting shafts as rotatingshafts and with the second supporting shafts as opening slide shaftsassisting the swinging movement of the guard panel. Accordingly, theguard panel 44 (or 64) can be swung satisfactorily.

The rear edge 50 (or 61) of each of the end pieces of the guard panel 44(or 64) or curved about the first supporting shaft 48 (or the secondsupporting shaft 62). Therefore, the slide member 57 is maintained insliding contact with the rear edge until the guard panel 44 (or 64) isfully swung. Accordingly, the guard panel 44 (or 64) is stably swung.

The panel opening mechanism for operating the guard panel 44 (or 64) isconsiderably simple in construction. Therefore, employment of themagnetic tape cassette of this embodiment of the invention will not makethe magnetic tape recording and reproducing device intricate inconstruction.

The invention will further be described with reference to a fourthembodiment shown in FIGS. 9 through 12 of the accompanying drawings.

FIG. 9 is an exploded perspective view of a magnetic tape cassette ofthe fourth embodiment of the magnetic tape cassette of the fourthembodiment of the invention. FIGS. 10 and 11 are an enlarged explodedperspective view and an enlarged horizontal sectional view,respectively, showing essential parts of the magnetic tape cassette. Asconducive to a full understanding of this embodiment, FIG. 9 shows aguard panel suitably cut away.

In FIG. 9, the magnetic tape cassette 71 is substantially equal in sizeto a conventional Philips-type magnetic tape cassette, and includes acassette case 72 made up of the upper and lower halves. A rectangularopening 73 is formed in the front end wall of the cassette case 72. Thecassette case 72 has a pair of through-holes 86 extending vertically ofthe cassette. A guard panel 74 adapted to close the opening 73 iscoupled to the cassette case 72 in such a manner that is is swingablevertically of the cassette case. The opening 73 receives the recordingand reproducing head, the erasing head and the pinch roller of amagnetic tape recording and reproducing device. The pair ofthrough-holes 76 receives the capstans.

A magnetic tape T wound on a pair of hubs (not shown) is laid in thecassette case 72 in such a manner that is can run along the opening 73.The hubs, arranged at a pair of shaft-insertion holes 75, into which thedrive shafts of the magnetic tape recording and reproducing device areinserted. A shield board (not shown) for protecting the magnetic tapefrom external noise and a leaf spring with a pressure pad adapted topositively bring the magnetic tape into contact with the magnetic headduring signal recording and reproducing operations may be provided atthe opening 73.

The front end portions of the right and left side walls 79 of thecassette case 72 are set back inwardly of the cassette case 72 to formsteps 80. A shaft-receiving through-hole 81 for receiving a rotatingshaft 78 (described below) is formed in each of the steps 80. One of theright and left side walls (the right one in FIG. 9) has aspring-receiving groove 83 which has its bottom flush with the step 80and which extends along the center line which divides the side wall intothe upper and lower halves. The upper and lower halves of eachshaft-receiving through-hole 81 are symmetrical in configuration withrespect to the aforementioned center line. In other words, thethrough-hole 81 is in the form of the character "L" which is inclinedforwardly. The cassette case 72 has cuts 87 formed at oppostie ends ofthe front end wall thereof in such a manner that the cuts extend in thedirection of thickness of the cassette case 72.

The guard panel 74 is made up of a front piece 76 adapted to close theopening 73 and end pieces 77 with rotating shafts 78. The guard panel 74is substantially U-shaped in section. The rotating shafts 78 areprotrusions extending from the end pieces inwardly of the cassette. Eachrotating shaft 78 is made up of a base part 78a, a slide part 78b and anend part 78c. The base part 78a and the end part 78c are larger indiameter than the slide part 78b. The outside diameter of the slide part78b is smaller than the width l₁ of the shaft-receiving hole 81, and theoutside diameter of the base part 78a and the end part 78c is largerthan the width l₁. The distance between the base part 78a and the endpart 78c is slightly larger than the wall thickness l₂ of the step 80.

The guard panel 74 is maintained urged towards the cassette case by atension springs 85 provided in the spring-receiving groove 83. One endof the tension spring 75 is connected to a pin on the end puece 77 whichis closer to the cassette case than the rotating shaft 78, and the otherend is connected to a pin 84 at the inner part of the spring receivinggroove 83.

When the magnetic tape cassette 71 thus constructed is loaded in themagnetic tape recording and reproducing device, the guard panel 74 isswung upwardly by a panel opening mechanism 90 provided at the cassetteinsertion section of the device. The operation of the guard panel 74 bythe panel opening mechanism 90 will be described with reference to FIG.12.

The panel opening mechanism 90 is made up of a pair of plates which areengaged with the lower edge of the guard panel 74 at both ends, or aplate which is engaged with the lower edge of the guard panel at oneend. The panel opening mechanism 90 is provided at the inner part of thecassette insertion section.

While the magnetic tape cassette 71 inserted into the cassette insertionsection (by moving it in the direction of the arrow A) is being moveddownwardly (i.e., in the direction of the arrow B), the lower edge ofthe front piece of the guard panel 74 is engaged with the upper end ofthe panel opening mechanism 90 which extends along the vertical cut 87of the cassette case 72. As the magnetic tape cassette 71 is furthermoved downwardly (in the direction of the arrow B), the guard panel 74is turned (in the direction of the arrow C) with the rotating shafts 78being slid upwardly along the shaft-receiving holes 81. After themagnetic tape cassette 71 has been completely loaded (moved in thedirection of the arrow B), the guard panel 74 is held open upwardly bythe panel opening mechanism 90.

The upper end portion of the panel opening mechanism 90 is suitablytapered so that, when the guard panel has been opened, it may not bedisplaced towards the cassette case by the elastic force of the tensionspring 85.

After the guard panel 74 has been swung upwardly to open the opening 73of the cassette case 72, the magnetic tape T can be subjected to arecording or reproducing operation. In unloading the magnetic tapecassette 71 from the magnetic tape recording and reproducing device, themagnetic tape cassette 71 is moved with strokes opposite to those inloading it. Therefore, the guard panel 74 is disengaged from the panelopening mechanism 90 so that the tension spring 85 causes the guardpanel 74 to completely close the opening (the guard panel 74 being swungin the direction opposite to the direction of the arrow C).

Therefore, when the guard panel 74 has closed the opening 73, therotating shafts 78 thereof are held abutted against the rear walls ofthe bends of the respective shaft-receiving holes 81.

Each shaft-receiving hole 81 is divided into upper and lower halves bythe upper and lower cassette halves. Therefore, the guard panel 74 canbe readily coupled to the cassette case 72 when the upper and lowercassette halves are combined together to form the cassette case 72.

The material of the cassette 72 is not particularly limited; that is, itmay be made of plastic material such as polyacetal or ABS resin. Theguard panel 74 may be made of plastic resin such as polyacetal or metal;however, it is desirable that it be made of a material high in wearresistance because the rotating shafts 78 slide along theshaft-receiving holes 81.

The magnetic tape T may be a ferromagnetic iron oxide or chromiumdioxide tape; however, it is preferabe to use a metal tape orvacuum-deposited tape suitable for high-density signal recording andreproducing operations.

As each rotating shaft 78 has a base part 78a, the contact area with theouter surface of the step is small during the guard panel swingingoperation and the end part 78c prevents the rotating shaft 78 fromcoming out of the shaft-receiving hole 81,

The magnetic tape cassette 71 is so formed that the upper and lowerhalves thereof are symmetrical in configuration and construction witheach other. Therefore, even if the magnetic tape cassette 71 is loadedin the recording and reproducing device with the upper side underneath,the guard panel is operated in the same manner. That is, both sides (Aand B sides) of the magnetic tape cassette can be used for signalrecording and reproducing.

In the above-described embodiment, the guard panel is opened as themagnetic tape cassette 71 is moved (in the direction of the arrow B).However, the cassette 71 may be loaded in a magnetic tape recording andreproducing device in which the panel opening mechanism 90 is movedvertically. It goes without saying that an elastic member such as thetension spring 85 may be provided on both of the right and left sidewalls of the cassette.

As described above, the magnetic tape cassette of the invention has theguard panel 74 which can be readily swung both upwardly and downwardly.Therefore, the magnetic tape cassette of the invention is most suitablefor a multi-track signal recording and reproducing operation in whichboth sides (A and B sides) thereof are used in the stationary headsystem.

When the magnetic tape cassette of the invention is unloaded from therecording and reproducing device, the guard panel 74 completely closesthe opening 73 of the cassette case 72 immediately. Therefore, themagnetic tape T laid along the opening 73 of the cassette case isprotected from damage and protected from the adverse effects of dust.Thus, the signal recording and reproducing characteristics of themagnetic tape T are maintained unchanged.

As each rotating shaft 78 has the base part 78a and the end part 78c,when the guard panel 74 is swung, the friction with the step 80 issmall, and the rotating shaft 78 is prevented from coming out of theshaft-receiving hole 81. Thus, the guard panel 74 can be positivelyoperated at all times.

The invention will be further described with reference to a fifthembodiment shown in FIGS. 13 through 17 of the accompanying drawings.

FIG. 13 is an exploded perspective view showing an example of a magnetictape cassette according to the fifth embodiment of the invention. FIG.14 is an exploded perspective view showing essential parts of themagnetic tape cassette in FIG. 13. As conducive to a full understandingof this embodiment of the invention, FIG. 13 shows a guard panel whichis suitably cut away.

The magnetic tape cassette 101 shown in FIG. 13, as in the previouslydiscussed embodiments, is substantially equal in size to theconventional Philips-type magnetic tape cassette. The magnetic tapecassette 101 is composed of a cassette case 102 made up of upper andlower cassette halves. The cassette case 102 has a rectangular opening103 in the front end wall thereof, and a pair of through-holes 116 whichextend vertically of the cassette. The cassette 101 further includes aguard panel 104 adapted to close the opening 103 and which is coupled tothe cassette case 102 in such a manner that it is swingable verticallyof the cassette. The opening 103 receives the recording and reproducinghead, the erasing head and the pinch roller of a magnetic tape recordingand reproducing device, and the pair of holes 116 receive the capstans.

A magnetic tape T wound of a pair of hubs (not shown) is laid in thecassette case 102 in such a manner that it runs across the opening 103.The hubs are arranged at a pair of shaft-receiving holes 105 into whichthe drive shafts of the magnetic tape recording and reproducing deviceare inserted. A shield board (not shown) for protecting the magnetictape from external noise and a leaf spring with a pressure pad adaptedto positively bring the magnetic tape into contact with the magnetichead during recording and reproducing may be provided at the opening103.

The guard panel 104 is made up of a front piece 106 and end pieces 107,being substantially U-shaped in section. A rotating shaft 108 extendsfrom each end piece 107 inwardly of the cassette. By means of therotating shafts 108, the guard panel 104 is coupled to the cassette caseto close the opening 103. A sleeve 118 made of resin such as POM ornylon or a metal having a high wear resistance is fixed on each rotatingshaft 108. The guard panel 104 is urged towards the cassette case by atension spring 105 arranged on one of the right and left side walls 109of the cassette case 102 so that the guard panel 104 is swingablevertically of the cassette.

The front end portions of the right and left side walls 109 are set backinwardly of the cassette case to form steps 110. One of the right andleft side walls 109 has a spring-receiving groove 113 which has itsbottom flush with the step 110 and which extends along the center linewhich divides the side wall 109 into upper and lower halves. A pair ofshaft-receiving through-holes 111 are formed in the steps 110 so thatthe rotating shafts 108 with the sleeves 118 can slide along the holes111 vertically of the cassette. More specifically, the upper and lowerhalves of each hole 111 are symmetrical in configuration with respect tothe aforementioned center line; in other words, the hole 11 is in theform of the character "L" which is inclined forwardly.

The cassette case 102 has cuts 117 formed respectively at both ends ofthe front end wall thereof extending in the direction of thickness ofthe cassette case 102.

One end of a tension spring 115 is connected to a pin at the rear end ofone of the end pieces 107 of the guard panel 104 (the right end piece107 in FIG. 13), and the other end is connected to a pin 114 provided atthe inner part of the spring-receiving groove 113 so that the guardpanel 104 is maintained urged towards the cassette case by the tensionspring 115. When the guard panel 104 closes the opening 103, therotating shafts 108 are held abutted against the bends of thethrough-holes 111.

The cassette case 102 may be made of plastic resin such as polyacetal orABS resin similarly as in the conventional cassette case; that is, thematerial of the cassette case 102 is not particularly limited. It isdesirable that the guard panel 104 be made of plastic resin such aspolyacetal which facilitates the manufacture and is relatively low incost.

The magnetic tape T may be a ferromagnetic iron oxide or chromiumdioxide tape; however, it is preferable to use a metal tape orvauum-deposited tape suitable for high-density signal recording andreproducing operations.

When the magnetic tape cassette 101 thus constructed is loaded in themagnetic tape recording and reproducing device, the guard panel 104 isswung upwardly by panel opening mechanism 120 provided in the cassetteinsertion section of the device.

The operation of the guard panel 104 by a panel opening member 120 willbe described with reference to FIGS. 15 and 16.

The panel opening member 120 is in the form of a plate which is engagedwith one of the right and left end portions of the guard panel 104 andis located at the inner part of the cassette insertion secton of therecording and reproducing device.

While the magnetic tape cassette 101 inserted into the cassetteinsertion section (by moving it in the direction of the arrow C) isbeing moved downwardly (i.e., in the direction of the arrow D), thelower edge of the front piece 106 of the guard panel is caused to abutagainst the upper end of the panel opening member 120. This abutmenttakes place when the cut 117 aligns with the panel opening member 120.As the magnetic tape cassette 101 is further moved (in the direction ofthe arrow D), the guard panel 104 is swung (in the direction of thearrow E) while the rotating shafts 108, on which the sleeves 118 arecarried, are slidably moved up the inclined walls 112 of theshaft-receiving through-holes 111. When the magnetic tape cassette 101has been loaded, i.e., when the movement of the cassette in thedirection of the arrow D has been accomplished, the guard panel 104 ismaintained opened upwardly by the panel opening member 120.

After the guard panel 104 has been swung upwardly to open the opening103 as described above, the magnetic tape T can be subjected to a signalrecording or reproducing operation. In unloading the magnetic tapecassette 101 from the recording and reproducing device, the cassette 101is moved with strokes opposite to those in loading it so that the guardpanel 104 is disengaged from the panel opening member, and therefore thetension spring 115 causes the guard panel 104 to completely close theopening (the guard panel 104 being swung in the direction opposite thedirection of the arrow E).

The upper and lower halves of the magnetic tape cassette 101 aresymmetrical in configuration and in construction, as is apparent fromthe above description. Therefore, even when the cassette is loaded inthe recording and reproducing device with the upper side underneath, theguard panel is operated in the same manner. That is, both sides (A and Bsides) of the cassette can be used for signal recording and reproducing.

In the above-described embodiment, the guard panel 104 is opened as themagnetic tape cassette 101 is moved (in the direction of the arrow D).However, the cassette 101 may be loaded in a magnetic tape recording andreproducing device in which its panel opening mechanism 120 is movedvertically.

In the above-described embodiment, each shaft-receiving through-hole 111is in the form of the character "L" inclined forwardly; however, theinvention is not limited thereto or thereby. For instance, the cassettemay be modified by, instead of the above-described shaft-receivingthrough-holes 111, employing holes elongated in the front-to-reardirection of the cassette that the guard panel 104 is swung verticallyby moving the rotating shafts 108 (on which the sleeves 118 are put)forwardly of the cassette. In this case, it is necessary to providemeans for moving the guard panel 104 forwardly of the cassette in thecassette insertion section of the recording and reproducing device.

In the above-described embodiment, the sleeves 118 is fixedly mounted onthe rotating shafts 108; however, the invention is not limited theretoor thereby. For instance, the sleeve 118 may be rotatably mounted on therotating shafts 108. In this case, the sleeve 118 is loosely mounted onthe rotating shaft 108, and then the end portion of the rotating shaft108 deformed so as to be larger in diameter.

Furthermore, in the above-described embodiment, the through-holes 111formed in the steps are used to receive the rotating shafts; however,the through-holes 111 may be replaced by L-shaped recesses.

The sleeve 118 described above may be modified as shown in FIG. 17. Asleeve 118a in FIG. 17 has flanges at both ends, the diameter of whichis larger than the width of the shaft-receiving through-hold 111.Similarly as in the sleeve 118, the sleeve 118a is fixedly mounted onthe rotating shaft or it is rotatably mounted thereon.

With the sleeves 118a, the inner surfaces of the end pieces 107 willdirectly contact the steps 110, which eliminates the difficulty that,when the guard panel 104 is swung, the inner surfaces of the end pieces107 rubs the steps 110 to create resin powder.

As is apparent from the above description, the magnetic tape cassette ofthe invention includes the guard panel 104 which can be readily swungboth upwardly and downwardly. Therefore, the magnetic tape cassette ofthe invention is most suitable for multi-track signal recording andreproducing in which both sides (A and B sides) of a magnetic tapecassette are used in the stationary head system.

When the magnetic tape cassette of the invention is unloaded from therecording and reproducing device, the guard panel 104 completely closesthe opening 103 of the cassette case 102 immediately. Therefore, themagnetic tape T laid along the opening 103 of the cassette case isprotected from damage and protected from the adverse effects of dust.Thus, the signal recording and reproducing characteristics of themagnetic tape T are maintained unchanged.

According to the invention, each rotating shaft 108 is covered with thesleeve 118 or 118a. Therefore, the difficulty that, when the guard panel104 is swung, the end pieces thereof rub the steps having theshaft-receiving through-holes of recesses 111 to create resin powder iseliminated. The wear of the rotating shafts 108 are minimized by the useof the sleeves 118 or 118a, which allows the guard panel to operatesatisfactorily for long periods.

A sixth embodiment of the invention will be described with reference toFIGS. 18 through 22 of the accompanying drawings.

FIG. 18 is an exploded perspective view showing a sixth embodiment of amagnetic tape cassette according to the invention. FIG. 19 is a verticalsectional view showing essential parts of the cassette. As conducive toa full understanding of the invention, a guard panel suitbly cut away isshown in FIG. 18.

The magnetic tape cassette 121 in FIG. 18 is substantially equal in sizeto the conventional Philips-type magnetic tape cassette and includes acassette case 122 made up of the upper and lower cassette halves. Thecassette case 122 has a rectangular opening 123 in its front end wall138, and a pair of through-holes 136 extending vertically of thecassette. A guard panel 124 adapted to close the opening 123 is coupledto the cassette case 122 in such a manner that is is swingablevertically of the cassette. The opening 123 receives the recording andreproducing head, the erasing head and the pinch roller of a magnetictape recording and reproducing device and the pair of through-holes 136receive the capstan.

A magnetic tape T wound of a pair of hubs (not shown) is laid in acassette case 122 in such a manner that it can run along the opening123. The hubs are arranged at a pair of shaft-receiving holes 125 in theconventional manner into which the drive shaft of the recording andreproducing device are inserted. A shield board (not shown) forprotecting the magnetic tape from external noise and a leaf spring witha pressure pad adapted to bring the magnetic tape positively intocontact with the magnetic head during signal recording and reproducingoperations may be provided at the opening 123.

The upper and lower edges of the front end wall 138 of the cassette case122 are chamfered at a suitable angle; that is, the front end wall 138has slopes 139 extending along the upper and lower edges thereof. Theangle is determined according to conditions, for instance, by a forcefor urging a guard panel 129 towards the cassette case. The front endportions of the right and left side walls of the cassette case 122 areset back inwardly of the cassette case to form steps 130. One of theright and left side walls (the right one in FIG. 18) has aspring-receiving groove 133 which has its bottom flush with the step 130and which extends along the center line which divides the side wall intoupper and lower halves. A pair of shaft-receiving through-holes 131 areformed in the steps 130. Each shaft-receiving through-hole 131 is in theform of the character "L" inclined forwardly. More specifically, theupper and lower halves of each shaft-receiving through-hole aresymmetrical in configuration with respect to the aforementioned centerline.

The cassette case 122 has a pair of cuts 137 at both ends of the frontend wall 138 thereof.

The guard panel 124 is made up of a front piece 126 adapted to close theopening 123 and end pieces 127, being substantially U-shaped inhorizontal section. The upper and lower edges 141 of the front piece 126are symmetrically extended towards the cassette case 122 in order toimprove the dust-proofing effect (FIG. 19). The right and left endpieces 127 have rotating shafts 128 at their centers, which extendinwardly of the cassette. With the rotating shafts 128 fitted in theshaft-receiving through-holes 131, the guard panel covers the opening123. A tension spring 135 is arranged in the spring-receiving groove 133formed in the cassette's side wall 129 to urge the guard panel towardsthe cassette case, thereby to permit the guard panel to swing. Morespecifically, one end of the tension spring 135 is connected to a pin atthe rear end of the end piece 127 (the right one in FIG. 18), and theother end is connected to a pin 134 at the inner part of thespring-receiving groove 133. Therefore, the guard panel 124 ismaintained urged towards the cassette case, and when the guard panel 124closes the opening, the rotating shafts 128 are abutted against thebends of the inclined-L-shaped through-holes 131.

The cassette case 122 may be made of plastic resin such as polyacetal orABS resin which is used to form a conventional cassette case. That is,the material of the cassette case 122 is not particularly limited. Theguard panel 124 may be made of plastic resin such s polyacetal or metl;however, it is desirable that it be made of a material which is elasticto the extent that the guard panel can be readily coupled to thecassette case 122. The magnetic tape T may be a ferromagnetic iron oxideor chromium dioxide tape; however, it is preferable to use a metal tapeor vacuum-deposited tape suitable for high-density signal recording andreproducing operations.

When the magnetic tape cassette thus constructed is loaded in therecording and reproducing device, the guard panel 124 is swung upwardlyby a panel opening member 140 which is provided in the cassetteinsertion section of the device.

The operation of the guard panel 124 by the panel opening member 140will be described with reference to FIGS. 20 and 21.

The panel opening member 140 is in the form of a plate which is engagedwith one of the right and left end portions of the guard panel 124 andis located at the inner part of the cassette insertion secton of therecording and reproducing device.

While the magnetic tape cassette 121 inserted into the cassetteinsertion section (by moving it in the direction of the arrow C) isbeing moved downwardly (i.e., in the direction of the arrow D), thelower edge 141 of the front piece 126 of the guard panel 124 is causedto abut against the upper end of the panel opening member 140. Thisabutment takes place when the cut 137 aligns with the panel openingmember 140. As the magnetic tape cassette 121 is further moved (in thedirection of the arrow D), the guard panel 124 is swung (in thedirection of the arrow E) while the rotating shafts 178 are moved up theinclined walls 132 of the shaft-receiving through-holes 121. In thisoperation, the guard panel is swung with the inner surface of the frontpiece 126 being in contact with the upper edge of the front end wall ofthe cassette case. When the magnetic tape cassette 121 has beencompletely loaded, i.e., when the movement of the cassette in thedirection of the arrow D has been accomplished, the guard panel 124 ismaintained open upwardly by the panel opening member 140 to open theopening 123.

The upper end portion of the panel opening member 140 is suitablytapered so that, when the guard panel has been swung, the guard panelmay not be displaced towards the cassette case by the elastic force ofthe tension spring 135.

After the guard panel 124 has been swung upwardly to open the opening123 as described above, the magnetic tape T can be adjusted to a signalrecording or reproducing operation. In unloading the magnetic tapecassette 121 from the recording and reproducing device, the cassette 121is moved with strokes opposite to the those in loading it so that theguard panel 124 is disengaged from the panel opening member 140.Immediately before the guard panel 124 completely closes the opening123, the lower edgge 141 of the front piece 126 of the guard panel isabutted against the lower slope 139 as shown in FIG. 21. Then, the guardpanel 124 is slid down the lower slope 139 (in the direction of thearrow F) by the elastic force of the tension spring to reach apredetermined position, thereby to completely close the opening. Whenthe guard panel 124 has completely closed the opening 123, the upper andlower edges of the guard panel 124 are in contact with the upper andlower slopes 139, respectively, of the cassette case 122 so that theguard panel 124 is fixedly held to close the opening 123.

In the above-described embodiment, the upper and lower edges of thefront end wall 138 are formed, in their entireties, into the upper andlower slopes 139, respectively. However, the objects of the inventioncan be achieved by forming parts of the upper and lower edges of thefront wall 138 into the upper and lower slopes 139.

Each of the upper and lower edges 141 of the guard panel 124 may be sodesigned that, as shown in FIG. 19, the thickness is larger towards thebase to increase the mechanical strength. In this case, it is necessarythat slopes 142 formed on the inside of the guard panel 124 be larger inthe angle of inclnation than the slopes 139 of the cassette case 122 topermit the guard panel 4 to close the opening 123 without forming a gaptherebetween.

The guard panel may be modified as shown in FIG. 22. In the guard panel143 in FIG. 22, the upper and lower edges 144 are partially recessed (asindicated at 145) at the position where the recording and reproducinghead (not shown), etc. are inserted into the cassette. When the guardpanel 143 is swung to fully open the opening 123, the angle of swing canbe smaller; that is, the guard panel 143 can fully open the opening 123with a smaller angle of swing. Therefore, the amount of verticalmovement of the cassette case 122 in the recording and reproducingdevice can be reduced, which contributes to miniaturization of therecording and reproducing device.

In the above-described embodiment, the guard panel is opened as themagnetic tape cassette 121 is moved (in the direction of the arrow D).However, the cassette 121 may be loaded in a magnetic tape recording andreproducing device in which the panel opening member 140 is movedvertically.

In the above-described embodiment, each shaft receiving through-hole 131is in the form of the character "L" inclined forwardly; however, theinvention is not limited thereto or thereby. All that is necessary forthe shaft receiving through-holes 131 is to have the above-describedinclined walls 132. It goes without saying that the shaft receivingthrough-holes 131 may be through-holes formed in the steps 130.

As is apparent from the above description, the magnetic tape cassette ofthe invention includes the gurd panel 124 (or 143) which can be readilyswung both upwardly and downwardly. Therefore, the magnetic tapecassette of the invention is most suitable for a multi-track signalrecording or reproducing operation using both sides (A and B sides) of amagnetic tape cassette in the stationary head system.

According to the invention, the cassette case 122 has the symmetricalupper and lower slopes 139 along the upper and lower edges thereof.Therefore, when the cassette 121 is unloaded from the recording andreproducing device, the guard panel 124 (or 143) is moved to theposition where it can completely close the opening 123. Therefore, thecassette 121 of the invention is considerably effective in protectingthe magnetic tape laid along the opening 123 from damage and from theeffects of dust. Thus, the signal recording and reproducingcharacteristics of the magnetic tape T can be maintained unchanged.

We claim:
 1. A magnetic tape cassette having a cassette case includingupper and lower halves, a front wall, and laterally opposed right andleft side walls, a magnetic head inserting opening in the front wall ofsaid cassette case, said case incorporating a pair of hubs on which amagnetic tape is wound, the improvement comprising:said cassette casehaving shaft-receiving holes respectively in said right and left sidewalls thereof, said cassette case shaft-receiving holes comprising twooppositely inclined elongated, intersecting grooves adjacent said frontwall and diverging towards the front wall, said intersecting groovesterminating at their intersection, and said cassette case being providedwith a guard panel for closing said opening, said guard panel beingsubstantially U-shaped and including a front piece and right angle endpieces at opposite ends of said front piece and having two shaftsfixidly mounted respectively to each of said end pieces, said shaftsbeing engaged with said elongated holes in such a manner that said guardpanel is vertically swingable about said shafts, and an elastic memberconnected between said guard panel and said cassette case to urge saidguard panel to close said opening with said shafts positioned in a planepassing through the intersection of said intersecting grooves; andwherein the two halves of said cassette case are symmetrical inconfiguration.
 2. A magnetic tape cassette having a cassette caseincluding upper and lower case halves, a front wall and laterallyopposed right and left side walls, a magnetic head inserting opening inthe front wall of said cassette case, said cassette case incorporating apair of hubs on which a magnetic tape is wound, the improvementcomprising:said cassette case further having shaft-receiving groovesrespectively in front end portions of said right and left side wallsthereof, each shaft-receiving groove having two intersecting inclinedgroove portions which terminate at their intersection, which divergetoward the front wall of said cassette case and which are symmetrical inconfiguration with respect to a line which divides said side wall intoupper and lower parts; a guard panel adapted to close said opening andbeing substantially U-shaped including a front piece and right and leftend pieces at opposite ends of said front piece, said guard panel havingshafts extending from inner surfaces of each said right and left endpieces in such a manner that said guard panel is swingable about saidshafts, said shafts being engaged with said shaft-receiving grooves; andbiasing means provided on one of said right and left side walls andconnected to a part of the respective end piece at a point closer to therespective free end of the guard panel than said rotary shaft andlocated along the center line of said guard panel to thereby urge saidguard panel towards said cassette case and said shafts towards theintersection of said inclined groove portions; and wherein: said upperand lower halves of said cassette case are symmetrical in configuration.3. A magnetic tape cassette having a cassette case including upper andlower case halves, a front wall, a rear wall and laterally opposed rightand left side walls, a magnetic head inserting opening in the front wallof said cassette case, said cassette case including a pair of hubs onwhich a magnetic tape is wound, the improvement comprising:said cassettecase having a slide groove extending in the direction from the frontwall toward said rear wall, and a guide groove having oppositelyinclined portions intersecting said slide groove and having oppositelyinclined guide groove portions formed within each of said right and leftside walls of said cassette case behind said opening; a substantiallyU-shaped guard panel having a front piece and a pair of end pieces atopposite ends of said front piece, each of said end pieces having firstand second supporting shafts arranged in line extending in saidfront-to-rear direction of said cassette case and being spaced apart forselective engagement with said slide groove and guide groove, said guardpanel being swingable vertically of said cassette case with one of saidfirst and second supporting shafts within said slide groove and theother shaft within said guide groove; and an elastic member connected tosaid guard panel to cause said guard panel to close said opening withthe spacing between said first and second shafts being such that withthe guard panel closed, the first and second shafts are both within saidslide groove and said guard panel is prevented from swinging verticallyof said said cassette case, and wherein: the two halves of said cassettecase are symmetrical in configuration and construction.
 4. The magnetictape cassette of claim 3, wherein said slide groove intersects saidguide groove at a middle portion of said slide groove.
 5. The magnetictape cassette of claim 3, wherein said slide groove intersects saidguide groove at an end of said slide groove adjacent said opening.
 6. Amagnetic tape cassette having a cassette case including upper and lowercase halves, a front wall, a rear wall and laterally opposed right andleft side walls, a magnetic head inserting opening in the front end wallof a cassette case, said cassette case incorporating a pair of hubs onwhich a magnetic tape is wound, the improvement comprising:said cassettecase having upper and lower slopes formed by symmetrically chamfering atleast parts of upper and lower edges of said front end wall,shaft-receiving holes being formed in the front end portions of saidright and left side walls of said cassette case; a U-shaped guard panelincluding a front piece and right and left end pieces at respective endthereof, said front piece of said guard panel having an upper and loweredges extending towards said cassette case so as to be engaged with saidupper and lower slopes, respectively, shaft fixedly extending from theinner surfaces of said right and left end pieces and engaged withinrespective ones of said shaft-receiving holes to permit said guard panelto swing about said rotary shafts and to open and close said opening;and urging means provided on at least of one said right and left sidewalls of said cassette case and connected to the respective one of saidend pieces at a position closer to said cassette case than said rotaryshaft of said respective one end piece to urge said guard panel towardssaid cassette case, said cassette case shaft receiving holes comprisingtwo oppositely inclined intersecting grooves diverging toward the frontwall of said cassette case and being symmetrical in configuration withrespect to a line dividing said cassette case into said upper and lowerhalves; such that said urging means causes said shafts to be positionedwithin the intersection of said inclined intersecting grooves with saidguard panel closing off said opening, and wherein the two sides of saidcassette are symmetrical in configuration and in construction.
 7. Themagnetic tape cassette of claim 6, wherein said guard panel has recessesat edges thereof at positions adjacent where a recording and reproducinghead is inserted into said cassette.